A novel IS element, IS621, of the IS110/IS492 family transposes to a specific site in repetitive extragenic palindromic sequences in Escherichia coli
A novel IS element, IS621, of the IS110/IS492 family transposes to a specific site in repetitive extragenic palindromic sequences in Escherichia coli
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DOI：
10.1128/jb.185.16.4891-4900.2003
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发表时间：
2003-08-01
影响因子：
3.2
通讯作者：
Ohtsubo, E
中科院分区：
文献类型：
--
作者：
Choi, S;Ohta, S;Ohtsubo, E
发现大肠杆菌菌株ECOR 28在其基因组中的10个位点处具有相同序列（长度为1，279 bp）的插入。该插入序列（命名为IS 621）具有一个大的开放阅读框，编码长度为326个氨基酸的推定蛋白质。使用DNA序列作为查询的计算机辅助同源性搜索显示，IS 621与piv基因同源，编码菌毛蛋白基因转化酶（PIV）。使用IS 621编码的推定蛋白质的氨基酸序列作为查询的同源性搜索显示，该蛋白质还与已知与PIV具有部分同源性的IS 110/IS 492家族元件编码的转座酶具有部分同源性。这表明IS 621属于IS 110/IS 492家族，但与piv基因最密切相关。事实上，基于PIV蛋白和转座酶的氨基酸序列构建的系统发育树显示，IS 621属于piv基因组，其不同于形成几个组的IS 110/IS 492家族元件。由IS 110/IS 492家族元件（包括IS 621）编码的PIV蛋白和转座酶具有四个酸性氨基酸残基，其在其N-末端区域中的位置是保守的。这些残基可能构成四联体D-E（或D）-D-D基序作为催化中心。有趣的是，IS 621被插入在ECOR 28基因组中10个位点的重复基因外回文（REP）序列内的特定位点。IS 621在转座中可能不识别整个REP序列，但它识别靶位点周围REP序列中保守的15-bp序列。有几个属于IS 110/IS 492家族的元件也转座到重复序列中的特定位点，如IS 621。IS 621不像大多数ISI 10/IS 492家族元件那样具有末端反向重复序列。IS 621的末端序列与PIV识别并用于菌毛蛋白基因倒位的菌毛蛋白基因倒位位点的26-bp反向重复序列具有同源性。这表明，IS 621通过识别其末端区域并在末端裂解来启动转座，其机制类似于PIV用于促进菌毛蛋白基因倒位位点的倒位。
An Escherichia coli strain, ECOR28, was found to have insertions of an identical sequence (1,279 bp in length) at 10 loci in its genome. This insertion sequence (named IS621) has one large open reading frame encoding a putative protein that is 326 amino acids in length. A computer-aided homology search using the DNA sequence as the query revealed that IS621 was homologous to the piv genes, encoding pilin gene invertase (PIV). A homology search using the amino acid sequence of the putative protein encoded by IS621 as the query revealed that the protein also has partial homology to transposases encoded by the IS110/IS492 family elements, which were known to have partial homology to PIV. This indicates that IS621 belongs to the IS110/IS492 family but is most closely related to the piv genes. In fact, a phylogenetic tree constructed on the basis of amino acid sequences of PIV proteins and transposases revealed that IS621 belongs to the piv gene group, which is distinct from the IS110/IS492 family elements, which form several groups. PIV proteins and transposases encoded by the IS110/IS492 family elements, including IS621, have four acidic amino acid residues, which are conserved at positions in their N-terminal regions. These residues may constitute a tetrad D-E(or D)-D-D motif as the catalytic center. Interestingly, IS621 was inserted at specific sites within repetitive extragenic palindromic (REP) sequences at 10 loci in the ECOR28 genome. IS621 may not recognize the entire REP sequence in transposition, but it recognizes a 15-bp sequence conserved in the REP sequences around the target site. There are several elements belonging to the IS110/IS492 family that also transpose to specific sites in the repeated sequences, as does IS621. IS621 does not have terminal inverted repeats like most of the ISI10/IS492 family elements. The terminal sequences of IS621 have homology with the 26-bp inverted repeat sequences of pilin gene inversion sites that are recognized and used for inversion of pilin genes by PIV. This suggests that IS621 initiates transposition through recognition of their terminal regions and cleavage at the ends by a mechanism similar to that used for PIV to promote inversion at the pilin gene inversion sites.